Concrete pavement and its construction



Jane 7, 1932. 8, B G E 1,862,011

CONCRETE PAVEilENT AND ITS CONSTRUCTION Filed Jan. :5, 1928 WITNESSES INVENTOR: W4. I BY jiobenffi. Gaye,

ATTORNEYS- Patented June 7, 1932 ROBERT B. GAGE, OF TRENTON, NEW JERSEY CONCRETE PAVEMENT AN D ITS CONSTRUCTION Application filed January '3, 1928. Serial No. 244,134.

layer or the wearing surface.

To give satisfactory service, a concrete pavement should consist of a substantially solid mass of concrete that is dense, reasonably uniform, and as free as possible from areas of poor cohesion, such as masses of segregated aggregate that are notfirmly cemented together. These requirements apply to the entire thickness of the pavement, from its wearing'surfaceto the lowermost portion of the concrete. In compound pavmg (as it may be termed), where a leaner concrete is used in the lower portion or foundation course than in the upper course or surface layer, it is very important (and in practice always specified) that the upper layer should adhere firmly to the lower course at all points. One example of such pavement is the type of construction generally employed in concrete sidewalks, where the wearing surface is usually a layer of rich sand and 0e ment concrete or mortar about one-half inch in thickness, while the base or foundation course is usually from three to four inches thick, and composed of a fairly lean concrete, including coarser aggregate than sand. Another e ample of compound pavement is the construction of reinforced concrete pavement in two or more layers or courses: i. e., a foun dation course is placed on the subgrade to the proper depth and struck or leveled off, the reinforcing metal is applied, and then the top layer of concrete is placed over the reinforcing metal, and finally struck off and consolidated. In this case, likewise, it is very important that the two courses of concrete be adequately united to one another, as well as to the reinforcing metal.

On the other hand, when a concrete pavement does ravel or start to disintegrate on the surface, the execution of satisfactory repair by replacing the defective top portion with new concrete is a difiicult and costly matter, owing to the difliculty of detaching the defective top portion of the concrete from the rest of the mass. Accordingly, the usual practice in such cases is first to repair all disintegrated places or holes in the pavement as a whole, and then to cover it with a layer of new concrete some three to four inches in 65 thickness. This, however, has the drawback that there is little or no adhesion between the new concrete and the old concrete, so that unless the new top layer is reinforced and is over three inches in thickness, it shows pre-' mature signs of failure and gives a very unsatisfactory life.

I have discovered away of constructing a concrete pavement to give the solidity of a monolithic mass through the whole thickness of the pavement, and at the same time to permit of easy resurfacing. My invention allows the original top layer or wearing surface to be made comparatively thin and inexpensive, and permits it to be easily removed, when it begins to fail, and replaced with an equally serviceable layer of similar thinness. In this way, the resurfacing costs very considerably less than by the usual method described above,often, indeed, fraction of the cost by that method.

For the purposes of my invention, I provide a bond of union between the lower course or foundation of the pavement and the upper layer or wearing surface that is strong enough to anchor the upper layer firmly, and thus, give the pavement the durability of a monolithic slab, and yet not so strong that the top layer cannot be removed rather easily when resurfacing becomes desirable,in other words, a plane of cleavage as well as of firm union or cementation, weaker than the concrete itself. This bond may be a cement of bituminous material, consisting of a layer or film of asphalt between the concrete courses or layers, firmly adherent to both of them.

The drawing shows a perspective or tilted view of a portion of a pavement conveniently embodying my invention. In carrying out my invention in practice, I may proceed as follows:

A lower layer or foundation course of concrete 5 is laid down and compacted on the subgrade in the usual manner. This course 5 only a 75 is then coated with aqueous bituminous emulsion, preferably applied before the concrete is fully dried, or even while it is quite perceptibly moist. Just after this has been done, and while the resultant asphaltic film 6 is itself still fresh and moist, the top layer or wearing surface of concrete 7 is laid down and consolidated as usual. The lower and upper concrete layers or courses 5, 7 may be either of the same composition or of different compositions, and in their combined thickness substantially equal to the desired total thickness of the pavement. The intermediate bituminous layer 6 need be no more than a mere film about inch thick or less.

B the time the concrete is fully set and hardened, so that the pavement is ready for service, the water in the bituminous emulsion will have dried out or been absorbed into the hydraulic cement of the concrete, and the bitumen 6 will remain as such and cement the upper layer 7 firmly to the lower layer 5. The joint 6 between the two layers will be waterproof, and will not be broken by traffic over the pavement: On the contrary, the bituminous bond will hold the top layer 7 firmly and prevent it from being shattered. When the upper layer or wearing surface 5 becomes defective, nevertheless, it can be easily broken up and removed without injury to the lower layer, owing to the inferior strength of the asphaltic bond 6 as compared with the concrete itself. During the process of breaking up and removing the upper layer 7, the asphalt 6 acts as a cushion to absorb shocks and prevent injury to the lower layer 5. After removal of the upper layer 7, the lower layer 5 can be recoated with asphaltic emulsion, and a fresh concrete upper layer applied in the same manner as the original one. Such newupper layer need be no thicker than the original one: i. e., not more than III an inch and a half to two inches, for exam lc,-and in some cases even less.

li ating thus described my invention, I claim: a

1. A. method of constructing pavement of the character described which comprises iaying down a concrete foundation layer; coating the same, while still fresh, with bituminous cement emulsion; and while this bituminous emulsion still fresh, laying down thereon a concrete wearing surface; so that after setting of the concrete, the bituminous cement will adhere firmly to both foundation and wearing surface, thus bonding them together as one slab.

2. A method of repairin a pavement comprising a concrete foun ation, a concrete wearing surface, and an intermediate layer of bituminous cement adherent to both foundation and wearing surfaces; which method comprises breaking up and removingthe concrete wearing surface; coating the thus exposed foundation with bituminous cement emulsion, and while this bituminous emulsion is still fresh, laying down thereon a new concrete wearing surface, so that after setting of the concrete, the bituminous cement will adhere and bond the same firmly to the foundation.

3. A pavement comprising a relatively thick concrete foundation and a relatively thin concrete wearing surface, with an intermediate layer of dried out bituminous cement emulsion applied Wet to the foundation and while still moist covered over with the concrete wearing surface, and thus firmly adherent to the wearing surface as well as to the foigidation and bonding them together as one sla In testimony whereof, I have hereunto signed my name at Trenton, New Jersey, this 27th day of December, 1927. i

ROBT. B. GAGE.

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